Fluid-controlled document transport drum



Sept. 9, 1969 JENSEN ETAL 3,466,029

FLUID-CONTROLLED DOCUMENT TRANSPORT DRUM Filed Dec. 26, 1967 3 Sheets-Sheet 1 2 ,H ,i F kflii 25a 1 a M :5 {will 2 m m a a L w: E: q E.L W2 52 M m $58 u m D .W. L N A S I N N o A D H K flW AT RNEY Sept. 9, 1969 JENSEN ETAL 3,466,029

FLUID-CONTROLLED DOCUMENT TRANSPORT DRUM Filed Dec. 26, 1967 3 Sheets-Sheet 2 Sept. 9, 1969 D. F. JENSEN ETAL 3,466,029

FLUID-CONTROLLED DOCUMENT TRANSPORT DRUM Filed Dec. 26, 1967 s Sheets-Sheet "United States Patent 3,466,029 FLUID-CONTROLLED DOCUMENT TRANSPORT DRUM Donald F. Jensen, Endicott, N.Y., and Hans R. Miiller,

Adliswil, Switzerland, assignors to International Business Machines Corporation, Armonk, N.Y., a corporation of New York Filed Dec. 26, 1967, Ser. No. 693,367 Int. Cl. B65h 5/06, 29/32 US. Cl. 271-51 11 Claims ABSTRACT OF THE DISCLOSURE A rotatable drum for attracting and releasing sheet material on the perforated cylindrical surface thereof by controlling internal diaphragm valve means to apply vacuum or pressure at the perforations in response to streams of pressurized fluid directed from stationary nozzles toward valve control ports on the drum periphery.

Cross-references to related applications Portions of the material herein disclosed have been disclosed and claimed in the following co-pending applications: Diaphragm-Type Fluid Logic Latch, Ser. No. 524,166, filed Feb. 1, 1966 by D. F. Jensen; and Apparatus Using Diaphragm-Type Fluid-Controlled Logic Devices and Method of Making Same, Ser. No. 412,405, filed Nov. 19, 1964 by R. E. Norwood.

Background of the invention Rotating vacuum drums are often used to transport or move sheet or web material by attracting the material to the drum surface by vacuum applied internally to ports on the drum surface. Release of the material is usually done by either mechanically peeling the material off the surface or terminating the applied vacuum. The latter method is preferred, and when used, control means, such as valves, are required with which the vacuum can be selectively connected and disconnected. The valve may be located internally of the drum or in the vacuum supply line to the drum.

The control of vacuum for rotating drums is particularly difiicultbecause of the high processing rates required for document handling machines. Valve actuation within the drum during rotation has been done by cam-operated valves without selective control, by the use of self-sealing members to block exposed ports, and by electromagnetically actuated valve levers for selective application of the vacuum. These methods have the disadvantages of requiring a vacuum source with a large capacity, slow response time or expensive, elaborate valves or controls therefor. The movement of relatively heavy members also adds weight and increases the response time and required operating energy.

When the vacuum is controlled by valves at its input to the drum, valve actuation is greatly simplified. However, the operating speed is decreased because of the time necessary to evacuate the lengthy path from valve to surface ports, or the large volume when the entire drum interior is evacuated. This method is also poorly suited to controlling two or more independent pluralities of surface ports when multiple documents are transported because each port plurality needs its individual vacuum control.

Accordingly, it is a primary object of this invention to provide a document transport drum in which vacuum is applied to surface ports with improved response time and simplified control.

Another object of this invention is to provide a document transport drum in which the application of vacuum to ports therein is controlled by fluid pressure externally of the drum during rotation.

Another object of this invention is to provide a document transport drum in which vacuum can be applied to separate pluralities of ports independently by pressurized fluid signals.

Yet another object of this invention is to provide a document transport drum in which documents are attracted to the drum surface by vacuum and released by reversing the direction of fluid flow.

A still further object of this invention is to provide document transport drum apparatus having diaphragmcontrolled valves applying vacuum to drum surface ports in response to streams of pressurized fluid directed toward the drum from stationary nozzles.

Summary of the invention The foregoing objects are attained with the invention by providing a rotatably supported drum having a cycontrolled valve means connected between the ports and a vacuum source which respond to streams of fluid for connecting the vacuum source to the ports. The valve means also includes means responsive to fluid streams for again disconnecting the vacuum source. The valve means is adapted to control the application of port pressures both above and below ambient pressure.

The diaphragm-controlled valve means lends itself to miniaturization so that the valves required for connecting and disconnecting vacuum and independently operating port groups can be compactly mounted within the drum. Diaphragm-controlled valves also have fast response speeds because of their size and can be operated with small fluid pressure differentials. This advantageously permits valve actuation without mechanical contact. In addition, ports can have vacuum applied successively since the fluid pressure actuating signals can be delayed to the respective control valves. By operating the vacuum ports with both vacuum and pressure, the ports are subject to the reverse flow of fluid and tend to be self-cleaning.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawmgs.

Brief description of the drawings FIG. 1 is a perspective view of document transport apparatus constructed in accordance with the invention;

FIG. 2 is a sectional view of a document transport drum shown in FIG. 1;

FIGS. 3, 4 and 5 are diagrams of fluid-operated, diaphragm-type valves arranged singly and in combination as used for the control of pressurized fluid in the transport apparatus; and

FIG. 6 is a diagram of the valve arrangement for controlling fluid flow for the selective pick-up and deposit of documents with the apparatus of FIG. 1.

Referring to FIG. 1, a document 10 is moved by conventional means, such as feed roll pair 11, toward rotating drums 12 and 13. The drums are driven at the same speed by a motor 14 in opposite directions as indicated by the arrows. Each drum has ports 15, 16 formed in the cylindrical surface to which a source of vacuum can be internally connected. On the approach of document 10 toward the periphery of drum 12, the vacuum at ports 15 adjacent the leading edge attracts the document to the drum surface. Continued rotation of the drum allows additional ports to grip successive portions of the document until the document is entirely supported on the drum.

While being carried by the drum, the document can move past a reading station 17 or be transferred to second drum 13. At times the data recorded on the drum must be reread, so that the document can be carried past the reading station two or more times, as required, before transfer.

The document is transferred from one drum to the other by terminating the vacuum applied at ports on drum 12 and, at the same time, internally applying vacuum to ports 15 on drum 13. Documents so transferred may pass a second station 18 for reading the reverse side of the document or performing an endorsement. Documents carried by drum 13 are transferred to document receiving means, such as feed rolls 19, for further processing or stacking.

Each drum 12 and 13 is connected to a negatlve pressure or vacuum source 20 and a positive pressure source 21 of fluid, such as air, pressurized above ambient pressure. The negative and positive pressures are both supplied through the hollow rotatable support shafts 22, 23 of respective drums 12, 13. Each drum contains valve means for selectively connecting either negative or positive fluid pressure to ports 15 on the drum surface. The control valves are illustrated in FIG. 3 and will be described subsequently.

The internal pressure control valves for the drums are actuated by timed streams of fluid from stationary external nozzle assemblies 24, 25. The assemblies direct the streams of fluid toward receiving valve control ports (not shown) located near the drum hubs. Each nozzle assembly 24 and 25 is connected by a respective duct 26 and 27 to a variable cycle control unit 28. Cycle control unit 28 combines input control signals with timing signals to produce the fluid streams issuing from the nozzle assemblies. The input signals may randomly occur in ducts 29 and 30 and can be generated by a reading or stacking station or other suitable device which produces pressure signals and indicates that another document should be processed. The timing signals may be generated by conventional means such as disc 33 with slots 34 therein. Fluid under positive pressure is continuously supplied from source 21 to nozzle 35 so that slots 34 periodically permit pressurized fluid to flow into receiving duct 37 leading to cycle control unit 28. By rotating disc 33 in timed relation with drums 12 and 13, accurately timed signals are produced by which the jet streams at nozzle assemblies 24 and 26 can be produced.

Cycle control unit 28 can be eliminated if the drum transport is to operate on a fixed cycle basis. In that case, the timing signals from disc 33 are supplied directly to ducts 26, 27 to operate the nozzle assemblies. The application and termination of vacuum to ports 15 or 16 would occur at regular intervals leaving no option for rescanning a document prior to transfer to the second drum or receiving means. The cycle control unit permits flexibility of cycle time and broadens use of the transport system.

The transport drums in FIG. 1 are each shown with two pluralities 15 and 16 of vacuum ports on the surface for accommodating two documents simultaneously. A separate control is necessary for each port plurality. A single stationary nozzle 24 or 25 can be used to direct the required control stream to the valve control ports on a drum hub. Each surface port plurality, however, has its own vacuum on-ofi ports properly spaced on the drum end for switching the vacuum. When transfer is to take place, a common signal can be used, for instance, to turn off the vacuum source at port plurality 15 on drum 12 and turn on the vacuum source at port plurality 15 on drum 13.

FIGURE 2 shows one manner of supplying negative and positive fluid pressures to the rotating drums, and the arrangement of the stationary nozzles and valve control ports. A drum 12 has an upright cylindrical document portion 40 fixed to horizontal end plate 41. The end plate is secured between internal hub 42 and external hub 43. External hub 43 has a threaded flange 44 and terminates below the flange in a taper. A sleeve 45 is formed with a complementary taper to accept the lower tapered portion of hub 43. The sleeve and hub are held together by a flanged threaded member 46 urging the two tapered elements into a tight seal. Sleeve 45 is supported in an upright position between low-friction bearings 47, 48 for rotation. The bearings are, in turn, mounted in a flanged housing 49 supported in upper base plate 50. A pulley 51 is fixed on sleeve 45 and driven by suitable means such as a belt. Interiorly of the sleeve is a duct 52 that is supported concentrically with respect to the sleeve. One end of the duct terminates at recess 53 in hub 42 and the other end is supported in the lower end of the sleeve 45 at hub 54 immediately below pulley 51. The duct extends below the pulley and is rotatably mounted in bearing 55 located in support block 56. The block is fastened to lower base plate 57.

Vacuum or negative pressure is supplied to the drum exteriorly by connecting the vacuum source to threaded opening 58 in housing 49. The housing and bearings 47, 48 provide an opening 59 between the housing and sleeve 45. The sleeve is formed with a plurality of slots 60 therein which connect the vacuum source with drum in terior via the interior of the sleeve between duct 52 and sleeve, and passageway 61 at the drum.

Positively pressurized fluid is supplied at threaded opening 62 in lower base plate 57 which communicates directly with duct 52. The pressurized fluid is directed to the drum interior via duct 52, recess 53 and passageway 63. Both the negative and positive pressures are connected to the valve means of FIG. 6 which is located inside the drum.

Control signals of pressurized fluid are supplied from one of the stationary assemblies 24 or 25 which comprises a nozzle 65 in block 66 on upper base plate 50. Fluid is selectively supplied from duct 26 toopening 67, and flows out nozzle 65 toward one or more control port slots 68 in lower hub 43. The control ports are formed by securing recessed annular disc 69 to hub 43. A duct 70 communicates with the slot to direct pressure signals to the interior valve means.

The valve means inside the drums are diaphragm-type fluid logic devices similar to those disclosed in US. Patent 3,318,329, issued May 9, 1967 to R. E. Norwood and assigned to the assignee of this application. Before proceeding with an explanation of the valve means, a brief description will be given of the logic devices employed in the control circuit. These devices are shown in FIGS. 3, 4 and 5. The devices generally employ diaphragm chambers in which the flow of fluid through a chamber is blocked by the closure of a flexible diaphragm against the fixed ridge within the chamber.

The device shown in FIG. 3 performs an amplifying function and is a basic element in the construction of fluid logic devices. Pressurized fluid from supply P flows via a duct through fluid resistance 71 which is a flow limiting orifice in the duct, through a diaphragm champer 72 between fixed ridge 73 and flexible diaphragm 74 and finally through a second fluid resistance 76 to a sump indicated as an exhaust pressure P Diaphragm chamber 72 is connected to a control duct 79 by which control signals of pressurized fluid can be applied to push flexible diaphragm 74 against ridge 73 and block fluid flow through the chamber. Resistors 71, 76 and the area ratio of the diaphragm in device 72 is selected so that the diaphragm device snaps closed at the desired predetermined control pressure level.

An output pressure tap 77 or 78 can be installed either upstream or downstream from the diaphragm chamber, depending upon whether signal inversion is desired. Resistances 71 and 76 are of a size to maintain the fluid pressure therebetween at approximately 60% of the supply pressure when device 72 is open for flow. If an input signal is applied at duct 79 that is sufficient to deflect the diaphragm against ridge 73, the downstream pressure below resistor 71, acting on a smaller diaphragm area, is insufficient to counteract the input signal and hence the diaphragm remains closed and the pressure rises at tap 77 until the full value of supply pressure is exhibited. The pressure at output tap 78, however, falls to the exhaust pressure because of the bleeding through resistor 76 to the sump. When the control signal at duct 79 terminates, the diaphragm opens allowing flow through chamber 72. The pressure at output tap 77 falls to approximately 60% of the supply pressure, while the pressure at tap 78 rises to approximately 60% of the supply pressure, depending upon the pressure drop through chamber 72. The output signals from taps 77 or 78 can be used to operate additional diaphragm devices such as shown in FIG. 4.

The logic device shown in FIG. 4 is an inverter circuit. The structural arrangement of the left-hand channel of the inverter is the same as that described with reference to 'FIG. 3. However, there has been added a parallel channel in which are located two diaphragm devices 80 and 81. It will be noted that there are no resistances in the right-hand channel. Assuming low pressure in duct 79, device 72 is open for flow so that the pressure in ducts 77 and 78 is approximately 60% of the supply pressure. The pressure in the channel containing devices 80 and 81 must drop from the supply pressure to the exhaust pressure through the devices and the ducts connecting them, since there are no restrictions in that channel. Because of this situation and suitably chosen diaphragm area ratios in devices 80 and 81, the pressure in channel duct 78 is sufficient to close the diaphragm in device 81, but the pressure in duct 77 is insufficient to close device 80. With device 80 open, the output ducts 82 exhibit the supply or high pressure. If a control signal is now applied to duct 79 to close device 72, the pressure in duct 77 rises to nearly that of the supply pressure closing device 80. The pressure in duct 78 bleeds to the exhaust opening the diaphragm in device 81, thereby allowing the pressure in output ducts 82 to drop to the exhaust pressure. Thus a low pressure present in duct 79 produces a high pressure output level in ducts 82 and, alternatively, a high pressure in duct 79 produces a low pressure signal in output ducts 82. In other words, the output pressure at ducts 82 will be the inverse of the input control pressure duct 79.

A latch arrangement of diaphragm devices is shown in FIG. 5. The first fluid path comprises a duct from supply P through resistance 84, diaphragm devices 85, 86 and resistance 87 to pressure P at the exhaust. The second parallel path comprises a duct from the supply pressure P through single diaphragm device 88 and resistance 89 to the exhaust pressure. Duct 90 connects the first path to the control chamber of device 88 and the output pressure levels are produced in ducts 91. Diaphragm device 88 diifers from those previously described in that its ridge 92 is located upstream a predetermined distance from the center position. This latch is similar to that described in the aforementioned U.S. patent application, Ser. No. 524,166 by D. P. Jensen. Assuming a control signal is present at duct 93 closing device 85, leaving device 86 open, exhaust pressure P exists in duct 90 so that device 88 is open and a high pressure level exists in output ducts 91. If the control input at device 85 is now removed, no change occurs in device 88 because the pressure acting on the ridge. side of the diaphragm is substantially at the supply pressure P and the pressure on the control side of the diaphragm is approximately 60% of the supply pressure. However, when a signal is present in duct 94 closing device 86, the pressure in duct 90 will assume that of the supply pressure and close the diaphragm in device 88 against ridge 92 due to the continued pressure drop across device 88 and resistance 89. At this time, the output pressure level in ducts 91 will decrease to the exhaust pressure P Once device 88 is closed, the control signal on device 86 may be removed and device 88- remains closed. This results from the fact that the pressure in duct 90 will return to approximately 60% of the supply pressure and act on the entire area of the control side of the diaphragm in device 88, while the supply pressure P acts only on the minor portion of the opposite side of the diaphragm upstream from ridge 92. In this condition, a low pressure signal exists in output ducts 91 until device is closed. The pressure in duct then becomes the exhaust pressure P enabling the supply pressure P acting on the minor area of the diaphragm to move the diaphragm away from ridge 92. At that time the output pressure level in ducts 91 will rise to the higher value. This latch thus exhibits a hysteretic effect and is referred to as a hysteresis latch herein.

The arrangement of the various diaphragm devices as the valve means is shown in FIG. 6. A stream of fluid under positive pressure issues from nozzle 65 in one of the nozzle assemblies in response to actuation by the cycle control unit 28. The jet stream produces a pressure buildup at passing aperture 68a which is actuated when documents are to be attracted to the drum surface. The transmitted valve control signal is applied to amplifier diaphragm device in a series of amplifiers 100, 101 and 102. The recovery pressure of the signal appearing at device 100 may be only a small value of the pressure range between the positive and negative supply pressures requiring multiple stages of amplification in order to obtain a reliable operating signal for the remainder of the circuit. In addition to the amplification, these stages provide a pulse-shaping function.

Amplifier 100 operates between a positive supply pressure inside the drum and atmospheric pressure obtained by connection to a vent to the drum exterior. Upon deflecting the diaphragm of device 100 against the blocking ridge, the positive supply pressure is applied to close the diaphragm of device 101, which is normally open. Device 101 has its exhaust connected between the available positive and negative supply pressures in order to obtain an exhaust pressure intermediate that of the supply and exhaust pressures. When device 101 closes in response to the output signals from the preceding stage, one of the parallel positive pressure channels to vacuum supply V is cut oil. This causes the input pressure to device 102 to fall allowing the normally closed diaphragm therein to open. The opening of device 102 creates a pressure rise in the output tap connected to device 103 in the hysteresis latch circuit.

The hysteresis latch, as described above with regard to FIG. 5, is comprised of input control devices 103 and 104 and output control device 105. At this time it may be assumed that device 104 is open and device 105 is closed, having been reset from the preceding operation. When device 103 closes in response to the high pressure signal from the preceding stage, the negative exhaust pressure through open device 104 allows device 105 to open so that the latch output switches to a high level. This condition remains until the latch receives a reset signal at diaphragm device 104 at the end of document transfer.

The high pressure signal from the latch closes device 106 at inverter 107. Signal inversion occurs at this stage to produce a negative pressure output signal at devices 108 and 109 and at delay 110. The low pressure is effective at device 108 of port valves 130 to open the diaphragm, permitting vacuum to be applied through ducts 111 and 112 to ports 15. The low pressure signal applied to device 109 permits the diaphragm to open for inverter 113 so that a high pressure output signal is produced to close the diaphragm at device 114 of port valves 130. The closure of diaphragm device 114 terminates the application of positive pressure P to channels 111 and 112 with the result that the vacuum now applied is etfective to attract a surface adjacent thereto.

The low pressure signal from inverter 107 and the high pressure signal from inverter 113 are applied to respective, similar delay chambers and 115. The delays in signal transmission need only be enlargements in the signal ducts sufiicient to cause the delay that is desired. Delayed signals to successive portions of the control valve ducts are used to successively apply vacuum to ports 15 as they arrive at the transfer point. This arrangement reduces the required capacity of the vacuum pump, and prevents sudden release of the entire document upon subsequent transfer.

The negative pressure signal passing through delay 110 is applied to input device 116 at inverter 117, and produces a high pressure output signal which is applied to device 118. The high pressure signal at device 118 of port valves 131 is effective to close the diaphragm therein and terminate the supply of positive pressure to ports 15 connected with ducts 119 and 120. In the meantime, the high pressure signal passing through delay 115 is applied at input device 121 of inverter 122 so that a negative pressure signal is applied at device 123 allowing the diaphragm to open and supply vacuum along ducts 119 and 120 to the connected document ports.

The termination of vacuum at ports 15 is accomplished by changing the level of the output signal from the hysteresis latch at device 105. When a document is to be released from the drum surface, a positive pressure jet is applied from nozzle 65 in timed relation with the appearance of receiver 68b. The high pressure signal from the receiver is applied to the series of amplifier stages 125, 126 and 127 similar to that for the above-described control signal at amplifiers 100, 101 and 102. The output signal from device 127 is applied to control device 104 for the hysteresis latch and is operable to close the diaphragm against the ridge in device 104. The supply pressure for the latch is then effective to close the diaphragm in device 105 so that a negative pressure signal is generated from the latch which is applied to inverter 107. The low pressure input to inverter 107 produces a reversal of signals from those described with regard to applying vacuum at the document ports so that the vacuum is terminated and the supply pressure is instead connected with the document ports. By applying a positive pressure that is above atmospheric, the documents are quickly deflected away from the drum surface and transfer rapidly occurs.

In order to provide for a large number of surface document ports in a ort plurality, the number of port valves on a control circuit is readily expanded by taking multiple output circuits from the inverter stages 107, 113, 117 and 122. Signal delay chambers are included to provide for the sequential control of successive ports. Each port plurality 15 or 16 (FIG. 1), however, will require its own logic control system of valves arranged to be independently operable by external input signals.

All connections requiring positive pressure supply P are made to a common manifold that is attached to duct 63 in FIG. 2. The requirements for negative pressure V can be met by leaving the exhaust restrictors for the diaphragm devices open to the drum interior. The drum interior is evacuated through duct 61 as described above. The document ports are each isolated from the drum interior by connection to the diaphragm devices with ducts; hence they are not open to the drum interior. The field logic devices used for the valve means can be compactly packaged within the drum since the diaphragm chambers and most of the interconnecting duct work between chambers can be inexpensively molded. A suitable construction method for the fluid logic devices is contained in the aforesaid patent application, Ser. No. 412,405 by R. E. Norwood.

It will be noted that both vacuum and positive pressures need not be supplied to the document ports but that operation can occur between ambient pressure, such as atmospheric, and the negative pressure. The arrangement wherein ositive pressure is used provides a significant advantage in that the ports are kept free of dirt by the flushing action due to the reverse flow of fluid, and, as noted above, there is the advantage of rapid document release when transfer occurs.

While the invention has been particularly shown and described with reference to a preferred embodiment 8 thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. Apparatus for transporting documents comprising:

a rotatably supported drum having a cylindrical surface with a plurality of openings in said surface; means providing a source of vacuum interiorly of said drum;

valve means having a receiving port at the exterior of said drum, said valve means being responsive to a fluid pressure signal at said port for connecting said vacuum source to said openings; and

means for directing pressurized fluid to said port as a said signal to effect connection of said vacuum. 2. Apparatus as described in claim 1 wherein: said valve means includes a second receiving port on said drum exterior and said valve means is responsive to pressurized fluid therein for disconnecting said vacuum source from said openings; and

said directing means includes means to direct pressurized fluid to said second port.

3. Apparatus as described in claim 1 wherein said valve means is mounted in said drum for rotation therewith.

4. Apparatus as described in claim 1 wherein said valve means and said port are moving relative to said fluid directing means.

5. Apparatus as described in claim 1 further including:

means for providing a source of fluid under pressure greater than ambient pressure to said valve means interiorly of said drum, said valve means being operable in the absence of said fluid signal for applying pressurized fluid to said openings to repel documents over said openings.

6. Apparatus as described in claim 1 wherein said valve means includes a plurality of devices having flexible diaphragms therein responsive to said signal for connecting said openings with said source of vacuum.

7. Apparatus as described in claim 1 wherein said receiving port diverges outwardly from said valve means to said drum exterior to effect an increase in the length of said signal.

8. Apparatus for transporting documents, comprising:

a rotatably supported drum having a cylindrical surface with at least a first and second plurality of openings in said surface;

means providing a source of vacuum interiorly of said drum; valve means in said drum for each said plurality of openings, each valve means having a receiving port at the exterior of said drum and responsive to pressurized fluid applied at said port for applying said vacuum source to the corresponding openings; and

means exterior of said drum for selectively directing pressurized fluid to said ports to effect connection of said vacuum to the desired plurality of said openings.

9. Apparatus as described in claim 8 including timing means for said directing means to apply said pressurized fluid to said ports synchronously with said drum rotation.

10. Apparatus as described in claim 8 wherein:

each said valve means includes a second receiving port and said valve means is responsive to pressurized fluid applied thereto for disconnecting said vacuum source from said openings; and

said directing means includes means for directing said pressurized fluid to said second ports.

11. Apparatus as described in claim 8 further including:

means for providing a source of fluid under pressure greater than ambient pressure to said valve means interiorly of said drum, said valve means being operable in the absence of said fluid signal for applying pressurized fluid to said openings to repel documents 3,227,441 1/ 1966 Fraidenburg 27174 over said openings. 3,318,329 5/1967 Norwood 137-599 References Cited RICHARD E, AEGERTER, Primary Examiner UNITED STATES PATENTS 5 US. Cl. X.R.

2,985,299 5/1961 Wiener 271-74 271-27374 

